Guitars are well known in the art and include a wide variety of different types and designs such as various types of acoustic and electric guitars. Guitar players and other musicians often modify the sound produced by the guitar to create a virtually endless variety of sounds. Example effects include: compression, tremolo, distortion, overdrive, fuzz, wah-wah, chorus, flange, phase shift, pitch shift, harmony, vibrato, delay (echo), reverberation (reverb), etc., which modify the audio signal produced by the guitar strings in various ways using mechanical, electrical, and electro-mechanical mechanisms.
A compression effect stabilizes the volume and “smooths” a note's “attack” by dampening its onset and amplifying its sustain and can be produced by varying the gain of a signal to ensure the volume stays within a specific dynamic range. A tremolo effect produces a slight, rapid variation in the volume of a note or chord. Tremolo effects normally have a “rate” knob, which allows a musician to change the speed of the variation. Distortion effects distort the tone of an instrument by adding “overtones”, creating various sounds such as a warm” sound or a “dirty” or “gritty” sound, which may be produced by re-shaping or “clipping” the sound waves produced so that they have flat, mesa-like peaks, instead of curved ones. Overdrive effects are similar to distortion effects except that an overdrive producing device produces “clean” sounds at quieter volumes and distorted sounds at louder volumes. A fuzz effect clips a sound wave until it is nearly a square-wave, resulting in a heavily distorted sound. A wah-wah effect results in vowel-like sounds, which are created by altering the frequency spectrum of the analog signal produced by the guitar. A chorus effect mimics the “phase locking” effect produced naturally by choirs and string orchestras when sounds with very slight differences in timbre and pitch assimilate with one another. A chorus effect splits the electrical signal, adding slight frequency variations to part of the signal while leaving the rest unaltered. A flange effect simulates a studio effect produced by holding the edge of the audio tape reel to momentarily slow down a recording. As a result, a flange effect adds a variably delayed version of the sound to the original sound creating a comb filter effect. A phaser causes a phase shift effect, which creates a slight rippling effect by adding out-of-phase duplicate sound-waves to the original sound-waves. A pitch shift effect raises or lowers (e.g. “transposes”) each note a musician plays by a pre-set interval. For example, a pitch shifter set to increase the pitch by a fourth raises each note four diatonic intervals above the notes actually played by the musician. A harmony effect is a type of pitch shift effect that combines the altered pitch with the original pitch to create a two or more note harmony. A vibrato effect produces slight, rapid variations in pitch, mimicking the fractional semitone variations produced naturally by opera singers and violinists when prolonging a single note. Vibrato effects often allow the musician to control the rate of the variation as well as the difference in pitch. A delay effect adds a duplicate electrical signal to the original signal at a slight time-delay. The effect can either be a single echo or multiple echoes. A reverb effect simulates sounds produced in an echo chamber by creating a large number of echoes that gradually fade or “decay”.
Additionally, other signal processing of the audio signals may remove or reduce noise. For example, a noise gate reduces “hum”, “hiss”, and “static” by eliminating sounds below a certain gain threshold. Still other signal processing utilizes an equalizer, which is a set of filters that strengthen or weaken specific frequency regions. For example, an equalizer may adjust the bass and treble and may be used to enhance particular aspects of an instrument's tone.
Application of the various sound effects can be applied using devices in the guitar itself and/or pedal boxes, amplifiers, mixers, etc. that receive the audio signals in either analog or digital form from the guitar. The application of the various sound effects may be controlled at the guitar and/or at the effects device. The guitar and/or effects devices may use digital signal processing (DSP) to apply the desired sound modifications to the analog sound produced by the guitar strings.
The analog signal varies in output level and impedance, is subject to capacitance and other environmental distortions, and can be subject to ground loops and other kinds of electronic noise. After being degraded in such fashion by the environment, the analog signal is often digitized at some point, with the digitized signal including the noise component. The analog or digital signal may be communicated to various other devices such as the effects devices at various points in the signal processing path.